Climate Effects of Volcanic Eruptions

7/29/2019 Climate Effects of Volcanic Eruptions

1/94

CLIMATE EFFECTS OF VOLCANIC ERUPTIONS

THE OZONE, GREENHOUSE, AND HAZE EFFECTS

There is considerable debate on the role that humans play inchanging global climate through both the burning of fossil fuels andthe release of chlorofluorocarbon (CFC) gases. Some argue thathuman interaction poses less of a threat to our atmosphere than donatural processes, like volcanic eruptions. This places a great deal ofimportance on understanding the role of volcanic eruptions inaffecting global climate change. Whatever the source, it is apparent

that compositionalchanges in the earth's atmosphere generate threeprincipal climatic effects:

THE OZONE EFFECT:

Intense sunlight in the stratosphere (above12 km) produces bluish colored ozone (O3)

by naturally breaking down normal oxygen

molecules (O2) into two highly reactiveoxygen atoms (O). Each oxygen atom thenquickly bonds with an oxygen molecule to

form ozone. Ozone absorbs UV radiation, and in the process ozone ischanged back into an oxygen molecule and an oxygen atom. A

balance exists in ozone destruction and production, so that anequilibrium concentration exists in the stratosphere. Thisequilibrium has probably existed throughout much of geologic time.

Recently, however, an ozone holehas been detected in thestratosphere over Antarctica, presumably due to the atmospheric

build up of ozone-destroying CFCs by humans. Ozone depletion hasresulted in a greater penetration of ultraviolet radiation on theearth's surface, which is harmful to life on earth because it damagescellular DNA. The ozone effectdoes not appear to have a directinfluence on global temperatures.

THE GREENHOUSE EFFECT:
http://www.geology.sdsu.edu/how_volcanoes_work/Thumblinks/ozone_page.htmlhttp://www.geology.sdsu.edu/how_volcanoes_work/Thumblinks/ozone_page.html


2/94

Certain gases, called greenhouse gases(primarily carbon dioxide and water vapor;

but also methane, N2O, and CFCs), allowshort wavelength radiation from the sun

(UV and visible light) to penetrate throughthe lower atmosphere to the earth's surface.

These same gases, however, absorb long wavelength radiation(infrared), which is the energy the earth reradiates back into space.The trapping of this infrared heat energy by these greenhouse gasesresults in global warming. Global warming has been evidentsince the beginning of the Industrial Revolution. Most scientists

attribute global warming to the release of greenhouse gases throughthe burning of fossil fuels.

THE HAZE EFFECT:

Suspended particles, such as dust andash, can block out the earth's sunlight,

thus reducing solar radiation andlowering mean global temperatures. Thehaze effect often generates exceptionallyred sunsets due to the scattering of red

wavelengths by submicron-size particlesin the stratosphere and uppertroposphere.

THE INFLUENCE OF VOLCANIC ERUPTIONS ONTHE OZONE, GREENHOUSE, AND HAZE EFFECTS

Volcanic eruptions can enhance all three of these climate effects tovariable degrees. They contribute to ozone depletion, as well as toboth cooling and warming of the earth's atmosphere. The role ofvolcanic eruptions on each climate effect is described below.

INFLUENCE ON THE OZONE EFFECT:


3/94

The halide acid HCl has been shown to be effective in destroyingozone; however, the latest studies show that most volcanic HCl isconfined to the troposphere (below the stratosphere), where it is

washed out by rain. Thus, it never has the opportunity to react with

ozone. On the other hand, satellite data after the 1991 eruptions ofMt.Pinatubo (the Philippines) and Mt. Hudson (Chile) showed a 15-20% ozone loss at high latitudes, and a greater than 50% loss overthe Antarctic! Thus, it appears that volcanic eruptions can play asignificant role in reducing ozone levels. However, it is an indirectrole, which cannot be directly attributed to volcanic HCl. Eruption-generated particles, or aerosols, appear to provide surfaces upon

which chemical reactions take place. The particles themselves do notcontribute to ozone destruction, but they interact with chlorine- andbromine-bearing compounds from human-made CFCs. Fortunately,volcanic particles will settle out of the stratosphere in two or threeyears, so that the effects of volcanic eruptions on ozone depletion areshort lived. Although volcanic aerosols provide a catalyst for ozonedepletion, the real culprits in destroying ozone are human-generatedCFCs. Scientists expect the ozone layer to recover due to restrictions

on CFCs and other ozone-depleting chemicals by the United NationsMontreal Protocol on Substances that Deplete the Ozone Layer.

However, future volcanic eruptions will cause fluctuations in therecovery process.

INFLUENCE ON THE GREENHOUSE EFFECT:

Volcanic eruptions can enhance global warming by adding CO2 to

the atmosphere. However, a far greater amount of CO2 iscontributed to the atmosphere by human activities each year than byvolcanic eruptions. Volcanoes contribute about 110 milliontons/year, whereas other sources contribute about 10 billiontons/year. The small amount of global warming caused by eruption-generated greenhouse gases is offset by the far greater amount ofglobal cooling caused by eruption-generated particles in thestratosphere (the haze effect). Greenhouse warming of the earth has

been particularly evident since 1980. Without the cooling influenceof such eruptions asEl Chichon (1982) andMt. Pinatubo (1991),
http://www-esd.worldbank.org/html/esd/env/org/mp/mp.htmhttp://www-esd.worldbank.org/html/esd/env/org/mp/mp.htm


4/94

described below, greenhouse warming would have been morepronounced.

INFLUENCE ON THE HAZE EFFECT:

Volcanic eruptions enhance the haze effect to a greater extent thanthe greenhouse effect, and thus they can lower mean globaltemperatures. It was thought for many years that the greatest

volcanic contribution of the haze effect was from the suspended ashparticles in the upper atmosphere that would block out solarradiation. However, these ideas changed in the 1982 after theeruption of the Mexican volcano, El Chichon. Although the 1980

eruption of Mt. St. Helens lowered global temperatures by 0.1OC, themuch smaller eruption of El Chichon lowered global temperaturesthree to five times as much. Although the Mt. St. Helens blastemitted a greater amount of ash in the stratosphere, the El Chichoneruption emitted a much greater volume of sulfur-rich gases (40xmore). It appears that the volume of pyroclastic debris emittedduring a blast is not the best criteria to measure its effects on theatmosphere. The amount of sulfur-rich gases appears to be more

important. Sulfur combines with water vapor in the stratosphere toform dense clouds of tinysulfuric aciddroplets. These droplets takeseveral years to settle out and they are capable to decreasing thetroposphere temperatures because they absorb solar radiation andscatter it back to space.

EXAMPLES OF GLOBAL COOLING IN THE AFTERMATH

OF HISTORIC ERUPTIONS:

Observational evidence shows a clear correlation between historiceruptions and subsequent years of cold climate conditions. Four

well-known historic examples are described below.

LAKI (1783) -- The eastern U.S. recorded the lowest-everwinter average temperature in 1783-84, about 4.8OC below the225-year average. Europe also experienced an abnormally

severe winter. Benjamin Franklin suggested that these cold


5/94

conditions resulted from the blocking out of sunlight by dustand gases created by the IcelandLaki eruption in 1783. TheLaki eruption was the largest outpouring of basalt lava inhistoric times. Franklin's hypothesis is consistent with

modern scientific theory, which suggests that large volumes ofSO2 are the main culprit in haze-effect global cooling.

TAMBORA (1815) -- Thirty years later, in 1815, the eruptionof Mt. Tambora, Indonesia, resulted in an extremely coldspring and summer in 1816, which became known as theyear without a summer. The Tambora eruption is

believed to be the largest of the last ten thousand years. New

England and Europe were hit exceptionally hard. Snowfallsand frost occurred in June, July and August and all but thehardiest grains were destroyed. Destruction of the corn cropforced farmers to slaughter their animals. Soup kitchens wereopened to feed the hungry. Sea ice migrated across Atlaniticshipping lanes, and alpine glaciers advanced down mountainslopes to exceptionally low elevations.

KRAKATAU (1883) -- Eruption of the Indonesian volcanoKrakatau in August 1883 generatedtwenty times the volume of tephrareleased by the 1980 eruption ofMt. St. Helens. Krakatau was thesecond largest eruption in history,dwarfed only by the eruption of

neighboring Tambora in 1815 (see above). For months afterthe Krakatau eruption, the world experienced unseasonablycool weather, brilliant sunsets, and prolonged twilights due tothe spread of aerosols throughout the stratosphere. The

brillant sunsets are typical of atmospheric haze. In London,the Krakatau sunsets were clearly distinct from the familiarred sunsets seen through the smoke-laden atmosphere of thecity. This is demonstrated in the painting shown here of a

sunset from the banks of the Thames River, created by artistWilliam Ascroft on November 26, 1883 (Courtesy of Peter


6/94

Francis). The unusual and prolonged sunsets generatedconsiderable contemporary debate on their origin.

PINATUBO (1991) -- Mt. Pinatubo erupted in thePhilippines on June 15, 1991, and one month later Mt. Hudsonin southern Chile also erupted. The Pinatubo eruptionproduced the largest sulfur oxide cloud this century. Thecombined aerosol plume of Mt. Pinatubo and Mt. Hudsondiffused around the globe in a matter of months. The datacollected after these eruptions show that mean worldtemperatures decreased by about 1 degree Centigrade over the

subsequent two years. This cooling effect was welcomed bymany scientists who saw it as a counter-balance to global

warming.

Climatic Research Unit:Information sheets

13: Volcanoes and their effect on climate

David Viner & Phil Jones

It has been known for some time that explosive volcanic eruptionscan have a major influence on global and regional climate. The most

well known eruption of recent times was Tambora, Indonesia, whichexploded in 1815. The following summer became known as the "the

year without a summer" in many parts of the Northern Hemisphere.

Only certain types of volcanic eruption will have an effect upon theclimate. The eruption has to be of sufficient magnitude to emit verylarge quantities of material into the lower stratosphere (20-25kmabove the Earth's surface) and, for maximum impact, it should be inlower latitudes. With these conditions met, the particles in the lowerstratosphere spread to form a "veil" over the whole planet. This veilthen affects the amount of the sun's energy which reaches theEarth's surface.Mt. St. Helens, which erupted in 1980, was large, but the main bulkof the ejected material emerged at a 45 angle rather than directlyupwards, so wasnt able to enter the stratosphere. Vast amounts of

material were deposited over the northern plains states of the US,
http://www.cru.uea.ac.uk/http://www.cru.uea.ac.uk/cru/info/http://www.cru.uea.ac.uk/http://www.cru.uea.ac.uk/cru/info/


7/94

but all the finer material was washed out by precipitation processeswithin a few weeks.

Benjamin Franklin, in 1783, first postulated that major volcaniceruptions affect climate, after the eruption of the Laki volcano inIceland. Ironically, most of the ejected material from this eruptionremained in the lower parts of the atmosphere, so Franklin had theright idea but the wrong volcano.

The Volcanic Effect on Climate

Past volcanic events provide a guide to the impact of majoreruptions.

In the upper four panels, Figure 1 shows the effects on global averagetemperatures of four low-latitude eruptions between the 1880s and1980s. Whilst the individual eruptions show a lot of variability in thetiming of the cooling (partly because the eruptions occur at differenttimes of the year) the average of the four, labelled "composite" in thefifth panel, shows significant cooling for many of the months in thesubsequent three years (particularly the boreal summers).

Major eruptions in lower latitudes are more climatically effective asthe veil is capable of reaching the higher latitudes of bothhemispheres, because of the nature of the atmospheric circulation.Material from major eruptions in the middle-to-high latitudes ofeach hemisphere tends to remain poleward of the eruption latitude.Major Icelandic or Alaskan/Aleutian/Kamchatkan eruptions,therefore, only influence the higher latitudes of the NorthernHemisphere.

Figure 1 also includes a similar hemispheric temperature history forthe period before and after the Pinatubo eruption in 1991. The

northern summers of 1992 and 1993 were the coolest of the periodfrom 1986 to the present.

The Spatial Patterns of Temperature Change

Whilst such large-scale averages provide good tests of climatemodels and of our theoretical understanding of the physical effects,forecasts like this are of little use unless we can also give somespatial detail.

Figure 2 - spatial pattern of cooling


8/94

This figure is also available as PostScript

Figure 2 shows the spatial pattern of the cooling for the twoextended summer seasons (March-October) following each eruption(i.e. the two years after each eruption). One plot is for the same four-

volcano composite, the other for Pinatubo. Cooling tends to be mostmarked over the continents and at middle-to-high latitudes, with thegreatest effects over eastern North America and northern andcentral Asia. Both Figures 1 and 2 are discussed in more detail inKelly et al. (1996).

Have Volcanic Eruptions Occurred More FrequentlyRecently?

The 20th century has only seen five major tropical eruptions.Another five have occurred at higher latitudes, giving a largeclimate-shaping eruption about every ten years. The eruptions have,however, not occurred at regular intervals. They all took place before1915 or after 1956. The in-between years were devoid of majoreruptions and this has probably been a contributing factor to the

global warming early this century, between 1920 and 1945 - thoughvolcanic effects can only be a part of the reason as northernhemispheric cooling began at least 10 years before the eruptionfrequency increased after 1956.

Was the 20th Century Unusual for Eruptions?

We have records back many centuries in some regions - millenniafor Italy and Japan because of the existence of written records - butin many regions such as the North Pacific and large parts of thetropics direct evidence is limited. Fortunately, the material in the
http://www.cru.uea.ac.uk/cru/info/volcano/fig2.pshttp://www.cru.uea.ac.uk/cru/info/volcano/fig2.gifhttp://www.cru.uea.ac.uk/cru/info/volcano/fig2.ps


9/94

veils eventually falls to Earth and an excellent record is preserved onthe ice caps of Greenland and Antarctica. We may not know wherethe eruption occurred but the frequency can be compared overseveral millennia.

These data show that the 20th century has seen more eruptions thansome centuries of this millennium but less than in the16th/17th/19th centuries. Volcanoes have probably, therefore, madea contribution to the cooler temperatures of these centuries, relativeto the 20th century (see The Millenial Temperature Record).

The Eruption of Mt Pinatubo, Philippines, June 1991

The eruption of Mt. Pinatubo in the Philippines in June 1991

provided an excellent opportunity to study the response of theclimate system to a major volcanic event.

Earlier work, from the 1960s onwards, suggested that when eruptionclouds reach the lower stratosphere (about 20-25km aloft) the dustspreads around over subsequent months forming a veil over theEarth. The veil slightly reduces the amount of incoming solarradiation reaching the surface, causing a cooling. The effects in theNorthern Hemisphere are greatest in the summer season because,then, the suns radiation levels are at their maximum. Cooling ismost pronounced over land regions because the thermal inertia ismuch smaller than over the oceans. The effects in the SouthernHemisphere are less and tend to spread out over a longer period.

Shortly after the eruption, when it was clearly evident that theeruption was of sufficiently large magnitude to eject material intothe lower stratosphere, scientists, led by Jim Hansen at NCAR in theUS, ran several model integrations from the period just before theeruption to about 5 years later.

The results showed good agreement with average surfacetemperatures over the Northern Hemisphere, highlighting thecooling in the northern summers of 1992 and 1993. After that time,

both the model and the observations returned to normal levels,continuing the slight upward trend of temperatures over the 1980-2000 period.

In many respects, this study can be considered as the first long-termforecast several seasons ahead.
http://www.cru.uea.ac.uk/cru/info/milltemp/http://www.cru.uea.ac.uk/cru/info/milltemp/


10/94

Impact apart, the importance of volcanic events is that forecasts canbe tested relatively quickly over the subsequent few years. Othernatural (e.g. solar output changes) and anthropogenic (increases ingreenhouse gases and sulphate aerosols) operate on decadal-to-

century timescales and any changes over short timescales are verydifficult to distinguish from the natural variability of the climatesystem. Volcanic-induced forcing is sufficiently large to be clearlyseen and provides a good test of climate model performance.

References

Kelly, P.M., Jones, P.D. and Jia Pengqun, 1996: The spatialresponse of the climate system to explosive volcaniceruptions.International Journal of Climatology 16(5), 537-

550

Pacaya

Country: Guatemala

SubregionName:

Guatemala

VolcanoNumber:

1402-11=

VolcanoType:

Complex volcano

VolcanoStatus:

Historical

LastKnownEruption:

2002

SummitElevation:

2552 m 8,373 feet

Latitude: 14.381N 1422'51"NLongitude: 90.601W 9036'4"W

Eruptions from Pacaya, one of Guatemala's most activevolcanoes, are frequently visible from Guatemala City, the nation'scapital. Pacaya is a complex basaltic volcano constructed justoutside the southern topographic rim of the 14 x 16 km PleistoceneAmatitln caldera. A cluster of dacitic lava domes occupies thesouthern caldera floor. The post-caldera Pacaya massif includesthe Cerro Grande lava dome and a younger volcano to the SW.

Collapse of Pacaya volcano about 1100 years ago produced adebris-avalanche deposit that extends 25 km onto the Pacific
http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-11=&VErupt=Y&VSources=Y&VRep=Y&VWeekly=Y&volpage=photo


11/94

coastal plain and left an arcuate somma rim inside which themodern Pacaya volcano (MacKenney cone) grew. A subsidiarycrater, Cerro Chino, was constructed on the NW somma rim andwas last active in the 19th century. During the past several

decades, activity at Pacaya has consisted of frequent strombolianeruptions with intermittent lava flow extrusion that has partiallyfilled in the caldera moat and armored the flanks of MacKenneycone, punctuated by occasional larger explosive eruptions thatpartially destroy the summit of the cone.

Fastest Glacier in Greenland

Doubles Speed 12.01.04

When people talkabout somethingmoving at a glacialpace, they arereferring to speedsthat make a tortoiselook like a hare.

While it is allrelative, glaciers

actually flow at speeds that require time lapses torecognize. Still, researchers who study Earth's iceand the flow of glaciers have been surprised to findthe world's fastest glacier in Greenland doubled itsspeed between 1997 and 2003.

Image to right: Jakobshavn Glacier Retreat

2001-2003: Jakobshavn Isbrae holds the record asGreenland's fastest moving glacier and majorcontributor to the mass balance of the continentalice sheet. Starting in late 2000, following a periodof slowing down in the mid 1990s, the glaciershowed significant acceleration and nearly doubledits discharge of ice. The following imagery from theLandsat satellite shows the retreat of Jakobshavn'scalving front from 2001 to 2003. Click on image to

view animation (1.9 MB). Click link below to see astill image of the retreating front over the past 150


12/94

years. High resolution still showing changes from1850 to 2003.High resolution still showing changes from 2001 -2003. Credit: NASA/USGS

The finding is important for many reasons. Forstarters, as more ice moves from glaciers on landinto the ocean, it raises sea levels. JakobshavnIsbrae is Greenland's largest outlet glacier, draining6.5 percent of Greenland's ice sheet area. The icestream's speed-up and near-doubling of ice flow

from land into theocean has increasedthe rate of sea levelrise by about .06millimeters (about .002 inches) per year,or roughly 4 percentof the 20th centuryrate of sea levelincrease.

Also, the rapid movement of ice from land into the

sea provides key evidence of newly discoveredrelationships between ice sheets, sea level rise andclimate warming.

The researchers found the glacier's sudden speed-up also coincides with very rapid thinning,indicating loss of ice of up to 15 meters (49 feet) inthickness per year after 1997. Along with increasedrates of ice flow and thinning, the thick ice that

extends from the mouth of the glacier into theocean, called the ice tongue, began retreating in2000, breaking up almost completely by May 2003.

Image to left:Break-up Causes AccelerationUpstream: As the Jakobshavn Glacier dischargesice from its mouth, tributary ice streams show signsof acceleration. This series of Landsat images from2002 shows rapid migration of ice features

downstream, triggering adjacent land ice toaccelerate downslope. Click on image to view
http://www.nasa.gov/101948main_calvingstill_1850_2003.tiffhttp://www.nasa.gov/101948main_calvingstill_1850_2003.tiffhttp://www.nasa.gov/101952main_calvingstill_2001_2003.tiffhttp://www.nasa.gov/101952main_calvingstill_2001_2003.tiffhttp://www.nasa.gov/101948main_calvingstill_1850_2003.tiffhttp://www.nasa.gov/101948main_calvingstill_1850_2003.tiffhttp://www.nasa.gov/101952main_calvingstill_2001_2003.tiffhttp://www.nasa.gov/101952main_calvingstill_2001_2003.tiff


13/94

animation (2.6 MB). Credit: NASA/USGS

The NASA-funded study relies on data fromsatellites and airborne lasers to derive ice

movements. The paper appears in this week's issueof the journal Nature.

"In many climate models glaciers are treated asresponding slowly to climate change," said IanJoughin, the study's lead author. "In this study weare seeing a doubling of output beyond what mostmodels would predict. The ice sheets can respondrather dramatically and quickly to climatechanges." Joughin conducted much of this research

while working at NASA's Jet PropulsionLaboratory, Pasadena, Calif. Joughin is currently aglaciologist at the Applied Physics Laboratory atthe University of Washington, Seattle.

The researchers used satellite and other data toobserve large changes in both speeds and thickness

between 1985 and 2003. The data showed that theglacier slowed down from a velocity of 6700 meters

(4.16 miles) per yearin 1985 to 5700meters (3.54 miles)per year in 1992.This latter speedremained somewhatconstant until 1997.By 2000, the glacierhad sped up to 9400

meters (5.84 miles)per year, topping out with the last measurement inspring 2003 at 12,600 meters (7.83 miles) per year.

Image to right: Greenland Ice Changes Since1990's: This visualization of laser altimetermeasurements from the mid 1990's shows overallthinning of Greenland's ice sheet, with thickeningin a few locations including the Jakobshavn

Glacier, where the ice stream slowed down in themid 1990s. More recent data show that the


14/94

Jakobshavn is now, in fact, retreating, and causingaccelerated thinning of adjacent ice at higherelevations in a manner that is consistent with itsacceleration. Cool colors represent areas of

thinning ice while warm colors show thickening.Slight inland thickening is attributed toaccumulation of atmospheric moisture frommelting ice at the coasts, supporting observationsof a greater net loss to the overall sum ofGreenland's ice cap. Click on image to viewanimation (6.7 MB). Credit: NASA

"This finding suggests the potential for moresubstantial thinning in other glaciers inGreenland," added Waleed Abdalati, a coauthorand a senior scientist at NASA's Goddard SpaceFlight Center, Greenbelt, Md. "Other glaciers havethinned by over a meter a year, which we believe istoo much to be attributed to melting alone. Wethink there is a dynamic effect in which the glaciersare accelerating due to warming."

Airborne laser altimetry measurements of

Jakobshavn's surface elevation, made previously byresearchers at NASA's Wallops Flight Facility,showed a thickening, or building up of the glacierfrom 1991 to 1997, coinciding closely with theglacier's slow-down. Similarly, the glacier beganthinning by as much as 15 meters (49 feet) a year

just as its velocity began to increase between 1997and 2003.

The acceleration comes at a time when the floatingice near the glacier's calving front has shown someunusual behavior. Despite its relative stability fromthe 1950's through the 1990s, the glacier's icetongue began to break apart in 2000, leading toalmost complete disintegration in 2003. Thetongue's thinning and breaking up likely reducedany restraining effects it had on the ice behind it, asseveral speed increases coincided with losses ofsections of the ice-tongue as it broke up. Recent

NASA-funded research in the Antarctic Peninsulashowed similar increases in glacier flow following


15/94

the Larson B ice shelf break-up.

Mark Fahnestock, a researcher at the University ofNew Hampshire, Durham, N.H., was also a co-

author of this study.

ARTICLE PARU DANS L'EDITION DU 18.09.04


16/94

A perspective on potential climate changes presented by Dr.Robert B. Gagosian, President and Director of Woods HoleOceanographic Institution

Over the past two decades, we have heard about greenhousegases and the idea that our planet is gradually warming. Id

like to throw a curveball into that thinkingspecifically the graduallywarming part.

This new thinking is little known and scarcely appreciated bypolicymakers and world and business leadersand even by the widercommunity of natural and social scientists. But evidence from severalsources has amassed and coalesced over the past 10 to 15 years. It points

to a completely differentalmost counterintuitivescenario.

Global warming could actually lead to a big chill in some parts of theworld. If the atmosphere continues to warm, it could soon trigger adramatic and abrupt cooling throughout the North Atlantic region

where, not incidentally, some 60 percent of the worlds economy isbased.

When I say dramatic, I mean: Average winter temperatures could drop

by 5 degrees Fahrenheit over much of the United States, and by 10degrees in the northeastern United States and in Europe. Thats enoughto send mountain glaciers advancing down from the Alps. To freezerivers and harbors and bind North Atlantic shipping lanes in ice. Todisrupt the operation of ground and air transportation. To cause energyneeds to soar exponentially. To force wholesale changes in agriculturalpractices and fisheries. To change the way we feed our populations. Inshort, the world, and the world economy, would be drastically different.

And when I say abrupt, I mean: These changes could happen within adecade, and they could persist for hundreds of years. You could see thechanges in your lifetime, and your grandchildrens grandchildren willstill be confronting them.

And when I say soon, I mean: In just the past year, we have seenominous signs that we may be headed toward a potentially dangerousthreshold. If we cross it, Earths climate could switch gears and jump

very rapidlynot gradually into a completely different mode ofoperation.


17/94

This is not something new under the Sun. It has happened throughoutEarths history, and it could happen again.

The key to these climate shifts is that Earths climate is created andmaintained by a dynamic system of moving, interacting parts. Earthsclimate system has two main components. The first one you are allfamiliar with by watching your local TV meteorologist or The WeatherChannel. It is the atmosphere, which circulates heat and moisturearound the globe. But, in fact, the atmosphere redistributes only abouthalf of the energy that the earth receives from the Sun.

The other half is transported around our planet by a circulation systemthat is equally important, but far less understoodthe ocean. The ocean

isnt a stagnant bathtub. It circulates heat around the planet like theheating and cooling system in your house. The atmosphere and oceansare equal partners in creating Earths climate. The atmosphere is arabbit. It moves fast. Rapid changes in atmospheric circulation causestorms, cold spells, or heat waves that play out over several days.

The ocean, on the other hand, is a turtle. It may take years or decades oreven millennia for similar disturbances to circulate through the ocean.But the ocean is a big turtle. It stores about 1,000 times more heat than

the atmosphere. So changes in ocean circulation can set the stage forlarge-scale, long-term climate changes.

One example that you may be familiar with is El Nio. Every few years,oceanic conditions shift, and surface water temperatures in the easterntropical Pacific get warmer. The atmosphere above the ocean shifts, too.El Nio rearranges worldwide wind and rainfall patterns, causingdestructive droughts, floods, storms, and forest fires. Not to downplay ElNio in the least, because it causes grave human suffering and billions ofdollars in damagebut El Nio is relatively short-lived. It lasts only a

year or two.

The climate changes Im concerned about last longer and involve theocean circulation system that spans the entire globewhich we oftencall the Great Ocean Conveyor.

The Great Ocean Conveyor is the oceans major heat-circulating system.The ocean keeps our planet from overheating by transporting heat northand south, from the equator to the poles, in currents traveling near the

ocean surface. In the Atlantic, the Conveyor removes heat from the


18/94

Southern Hemisphere and releases it to the Northern Hemisphere.

The most famous and most important of these currents is the Gulf

Stream. The vast Gulf Stream transports the equivalent volume of 75Amazon Rivers. It carries heat absorbed in the tropics, and moves up theEast Coast of the United States, then northeastward toward Europe.

When the Gulf Streams warm, salty waters reach colder latitudes, theygive up their heat to the atmosphere. The atmosphere in the North

Atlantic region warms by as much as 10 degrees Fahrenheit. Prevailingwinds carry the heat eastward into Europe. Thats one reason London,Englandwhich is located at the same latitude as Calgary and

Edmontonhas warmer winters than New Yorkwhich is hundreds ofmiles farther south.

When the Gulf Streams waters reach the Labrador, Greenland and othernorthern seas, and lose their heat to the atmosphere, they become colderand hence denser. The waters are also relatively salty. Salty water isdenser than fresher water, so the whole salty mass begins to sink togreat depths.

When this sinking mass of cold water reaches the abyss, it then flows atdeep levels of the ocean, from the North Atlantic southward into theSouth Atlantic. The plunge of this great volume of cold, salty waterpropels the Great OceanConveyor. And on the back end, itcreates a void that actively pullsthe Gulf Stream northward toreplace the waters that aresinking.

Its a pretty neat system. We havebeen operating under the climateconditions created by this

beneficent oceanic heating,ventilation, and cooling systemfor centuries.

But what if this system werentoperating today? What if cold

North Atlantic waters didnt sink

A schematic of theocean circulation

system, often called the GreatOcean Conveyor, that transportsheat throughout the world oceans.Red arrows indicate warm surfacecurrents. Blue arrows indicate deepcold currents. (Animation by JackCook, WHOI)


19/94

and warm equatorial waters werentdrawn in to replace the sinking

waters? Then the North Atlanticregion would be a much different,much colder place.

The vast majority of us go about ourbusiness thinking that Earthsclimate system has always been this

way, and always will be. But that isjust not the case. In fact, we knowthat the Ocean Conveyor has indeedshut downstopped operatingin

the past.

We know this by examining trulyinteresting and valuable naturalarchives that record past changes inEarths climate. For example, wecan see layers within ice sheets inGreenland or in high elevations inthe Andes Mountains in South

America. This layering is caused byvariations in the amount of snowthat fell on the top of the ice sheet in

the past.

The light and dark bands within the ice sheet show an annual cycle ofdust in the atmosphere, so each couplet reflects the amount of snow thatfell in one year. By analyzing the chemistry of the ice itself, scientists candetermine the temperature of the atmosphere when the snow was

produced.

Thus from a single ice sheet record, it is possible to reconstruct the pasthistory of precipitation and air temperature in a region. For very old icesheets, like the glaciers on Greenland, it is possible to reconstruct thisclimate history 100,000 years into the past.

The ocean has similar archives of past climate. By taking cores from theocean floor, it is possible to reconstruct the history of ocean climate back

many thousands of years. We have used our ships to collect samples of

The Great OceanConveyor is

propelled by the sinking of cold,

salty (and therefore denser)waters in the North AtlanticOcean (blue arrows). That createsa void that pulls warm, salty GulfStream waters northward (redarrows). The Gulf Stream givesup its heat to the atmosphereabove the North Atlantic Ocean,and prevailing winds (large redarrows) carry the heat eastward

to warm Europe. (Animation byJack Cook, WHOI)


20/94

sediments from the seafloor. Preserved in the sediments are the fossilremains of microscopic organisms that settle to the seafloor. Theyaccumulate over time in layerssimilar to the ice corethat delineatemany important aspects of past climate.

For instance, certain organisms are found only in colder, polar watersand never live in warmer waters. They can reveal where and when coldsurface waters existedand didnt existin the past.

From records like these, we know that about 12,800 years ago, NorthAtlantic waters cooled dramaticallyand so did the North Atlanticregion. This large cooling in Earths climate occurred in about a decade.

And the cold spell lasted for about 1,300 years.

This period is called the Younger Dryas, and it is just one of severalperiods when Earths climate changed very rapidly from warm to coldconditions, and then back to warm again. So these long-term cold snapsare not unusual.

These shifts almost certainly involved changes in the oceans circulation.There were shutdowns and restartings of the Ocean Conveyor. These

warm-to-cold transitions happen in about 3 to 10 years. The cold

periods lasted for 500 to 1,000 years. Such oscillations intemperature and ocean circulation have occurred on a regular basis.

About 1,000 years ago, during a period of unusually warm temperaturesin the North Atlantic, the Norse established settlements and vineyardsin Greenland that would not be possible today. Those settlements wereabandoned about 500 years ago, when we believe the most recentshutdown of the North Atlantic Ocean circulation system occurred.

During that era, called the Little Ice Age, northern Europe was muchcolder than it is today. Glaciers spread outward and downward in the

Alps. Winters, on average, were more severe. Farming was affected.Famine was frequent.

In the 1730s and 1740s, abrupt European cooling caused famine acrosswestern Europe, especially in Ireland and France, where farmersdepended on wheat and potatoes. In Ireland, this is known as theforgotten famine. As many people died during the forgotten famine asdied during the famed potato famine of the 1840s.


21/94


22/94

Another way to look at Earths climate system is a simple mode ofbalances (see diagram, left). Like most dynamic systems, Earths climateseeks a stable mode. And it will tend to stay in that mode if nothingcauses it to change. Thats the top tier of the diagram. The ball remainsensconced in its cup.

The middle tier shows what happens if you push on the system. The ballwill rattle and roll around in different directions for a while until itsettles back down in its cup. We humans would definitely notice thatrattling until the climate system returned to equilibrium. The balance,forced to move, staggers but recovers.

Then there is a third situation in which a strong enough push at the

right time could shove the system past a threshold and into a completelydifferent mode of operation. In terms of our climate system, that meansthat a small or temporary forcing could produce a sudden, large, andlong-lasting change. That begs the next question: What could do that toour climate system today?

One answer to that is fresh water. If you simply add too much freshwater to the North Atlantic, the waters there will become less salty andless dense. They will stop sinking. Then the Gulf Stream slows down or

is deflected southward. Winters in the North Atlantic region getsignificantly colder.

Now heres the predicament. In the past year, oceanographersmonitoring and analyzing water conditions in the North Atlantic, haveconcluded that the North Atlantic has been freshening dramaticallyespecially in the past decade. New data from Ruth Curry at WoodsHole Oceanographic Institution and her colleague Robert Dickson at theBritish Centre for Environment, Fisheries, and Aquaculture Sciencechronicles salinity changes in the western North Atlantic since 1960.

The Great Ocean Conveyor transports fresh surface water down into thedepths. The depths can absorb a lot of fresh water like a sponge. Butsince 1970, the equivalent of an extra 20 feet of fresh water across thesurface of the northern North Atlantic has been transported down intothe ocean depths, most of that since 1990.

A sponge that is three-quarters saturated can still absorb more water.But the moment that sponge is fully saturated, it can absorb no more

water.
http://www.alertes-meteo.com/glaciaire/glaciaire.htm#data%23datahttp://www.alertes-meteo.com/glaciaire/glaciaire.htm#data%23data


23/94


24/94

At some point, the North Atlantic will no longer absorb any more freshwater. It will begin to pile up on the surface. When that happens, theGreat Ocean Conveyor will be clogged. It will back up and ceasefunctioning.

The very recent freshening signal in the North Atlantic is arguably thebiggest and most dramatic change in ocean property that has ever beenmeasured in the global ocean. Already, surface waters in the GreenlandSea are sinking at a rate 20percent slower than in the 1970s.

At what percent will the OceanConveyor stop? 25 percent? 40

percent? 60 percent? This is not likea dimmer switch, but more like alight switch. It probably goes fromon to off.

We cant yet determine the precisesource or sources of this additionalfresh water. Global warming may bemelting glaciers, or Arctic sea ice. In

recent decades, the volume of Arcticsea ice has decreased by 40 percent.And if North Atlantic sinking slowsdown, less salty Gulf Stream watersflow northwardwhich exacerbatesthe situation.

In February 2002, at a worldwide meeting of oceanographers, new dataon North Atlantic freshening prompted many scientists to say thatsalinity levels in the North Atlantic are approaching a density very closeto the critical point at which the waters will stop sinking.

One of my colleagues at Woods Hole, Terry Joyce, put it this way: Imin the dark as to how close to an edge or transition to a new ocean andclimate regime we might be, he said. But I know which way we are

walking. We are walking toward the cliff.

To that sentiment, I would add this: We are walking toward the edge of acliffblindfolded. Our ability to understand the potential for future

abrupt changes in climate is limited by our lack of understanding of the

If too much freshwater enters the

North Atlantic, its waters couldstop sinking. The Great Conveyor

would cease. Heat-bearing GulfStream waters (red arrows wouldno longer flow into the North

Atlantic, and winters wouldbecome more severe. (Animationby Jack Cook, WHOI)


25/94

processes that control them.

New data shows that North Atlantic waters atdepths between 1,000 and 4,000 meters are

becoming dramatically less salty, especially inthe last decade. Red indicates saltier-than-normal waters. Blue indicates fresher waters.Oceanographers say we may be approaching athreshold that would shut down the GreatOcean Conveyor and cause abrupt climatechanges. (Data from Ruth Curry, WHOI, BobDickson, Centre for Environment, Fisheries,and Aquaculture Science and Igor Yashayaev,Bedford Institute of Oceanography)

In the past decades, we have made great strides in understandingEarths atmospheric circulation system because we established a global

network of thousands of meteorological stations to monitor changingatmospheric conditions. No observational network exists tocontinuously monitor the oceans. If we just had a few more strategicallyplaced modern instruments in the oceans for an extended time, we couldunderstand so much more about how the oceans can cause abruptclimate changes. At present, there is no national plan for improving ourunderstanding of the issue, and according to a 2002 National ResearchCouncil report, no policymaking body is addressing the many concernsraised by the potential for abrupt climate change.


26/94

So heres the situation: We have unequivocal evidence of repeated, large,widespread, abrupt climate changes on Earth. It is reasonable to assumethat greenhouse warming can exacerbate the possibility of precipitatinglarge, abrupt, and regional or global climatic changes. We even havestrong evidence that we may be approaching a dangerous thresholdthat we are squeezing a trigger in the North Atlantic.

We could downplay the relevance of past abrupt events and deny thelikelihood of future abrupt climate changes. But that could prove costly.

With growing globalization, the adverse impacts of climate changes arelikely to spill across national boundariesthrough migration, economicshocks, and political aftershocks.

Over human history, one of the major ways that humans have adaptedto changing environmental and economic fortunes has been to migratefrom unproductive or impacted regions to more productive andhospitable regions. But today, the worlds population has grown toolarge. There is less usable, unpopulated territory to absorb migrants.National borders are less open, so it is difficult for people to move toother countries when droughts, floods, famines, and wars occur. These

boundary effects could be particularly severe for small and poorcountries, whose populations are often unwelcome in richer countries.

In the 1840s, more than 1 million Irish people emigrated because of thepotato blight. Can you imagine an equivalent migration of many millionsof people today? Keep in mind that there were only about 1 billionpeople on Earth then. There are 6 billion now.

As a society, I believe we must face the potential for abrupt climatechange. Perhaps we can mitigate the changes. If not, at least we can stilltake steps to adapt to them.

The best way to improve the effectiveness of our response is to havemore knowledge of what can happenand how and when. Research intothe causes, patterns, likelihood, and effects of abrupt climate change canhelp reduce our vulnerabilities and increase our ability to adapt.

If climate changes come abruptly, we will have less time to adjust. Inother words, the more knowledge we havethe more reliably we canpredict changesthe better our chances.

Maybe over the edge of the cliff, theres just a three-inch drop-off. Or

maybe theres a big, fluffy bed full of pillows. My worry is that we are


27/94

indeed approaching this cliff blindfolded.

Are you comfortable and secure with this scenario?

SOURCE :http://www.whoi.edu/home/about/whatsnew_abruptclimate.html

The Heat Before the ColdBy Terrence JoycePublished in The New York TimesApril 18, 2002

This weeks unexpected heat wave across much of the Northeast and

Midwest, couple with recent reports about the surprisingly fast collapseof an Antarctic ice shelf the size of Rhode Island, has heightened fears oflong-term rise in temperatures brought about by global warming. Butthis fear may be misguided. In fact, paradoxically, global warming couldactually bring colder temperatures to some highly populated areas likeEastern North America and Western Europe.

Heres what might happen: In the North Atlantic, a 10-foot layer of freshwater - some of which may be coming from melting ice in the Arctic -has been accumulating and lowering the salinity of the ocean to depthsof more than a mile for the past 30 years. Fresh water in the ocean maynot sound cataclysmic, but it can upset the ocean currents that are thekey to our planets climate control system.

In February, oceanographers presented new evidence that this northernfreshwater buildup could alter currents in a way that would cause anabrupt drop in average winter temperatures of about 5 degreesFahrenheit over much of the United States and 10 degrees in theNortheast. That may not sound like much, but recall the coldest winters

in the Northeast, like those of 1936 and 1978, and then imaginerecurring winters that are even colder, and youll have an idea of whatthis would be like. This change could happen within a decade and persistfor hundreds of years.

Under normal circumstances, the famous warm waters of the GulfStream, carrying heat absorbed in the tropics, move up the East Coast ofthe United States and southeastern Canada and then angle towardEurope, warming the overlying atmosphere and surrounding land as

they go. As the Gulf Stream system carries warm, salty water north, the
http://www.whoi.edu/home/about/whatsnew_abruptclimate.htmlhttp://www.whoi.edu/home/about/whatsnew_abruptclimate.html


28/94

atmosphere cools it, making it dense enough to sink to great depths. Theplunge of that great volume of water helps propel a global system ofcurrents sometimes called the great ocean conveyor. But add too much

fresh water, and North Atlantic waters become less salty and less dense.They stop sinking. The Gulf Stream slows or is redirected southward.

Winters in the North Atlantic region get significantly colder.

Changes in the conveyor were responsible for some of the mostnoticeable climate changes in scientific history. About 12,000 years ago,as the earth emerged from the most recent Ice Age and the North

Atlantic region warmed, an influx of fresh water - perhaps from meltingice sheets - shut down the great conveyor and plunged much of the

Northern Hemisphere back into ice-age conditions that lasted 1,000years. About 500 years ago a reduction of the ocean conveyors may haveturned the climate in northern Europe and the northeastern UnitedStates much colder, during what became known as the Little Ice Age,

which lasted for about 300 years. In America, the Little Ice Agecoincided with the notorious winter at Valley Forge.

There is not enough evidence for scientists to know for sure whether theinflux of fresh water in the North Atlantic has come from an already

altered ocean circulation, changes in rainfall patterns or rivers, or glacialand Arctic Ocean ice. We dont know the exact threshold at whichsinking, and the great ocean conveyor, could stop. A global ocean-observing system would greatly enhance our ability to monitor changesthat can spawn major, long-lasting climate shifts like these and lead toreliable predictions of what may follow. But the evidence we do havesuggests that global warming could actually lead to a big chill.

Terrence Joyce is a senior scientist and chairman of the department ofphysical oceanography at Woods Hole Oceanographic Institution.

DISCOVER Vol. 23 No. 9 (September 2002)Table of Contents

The New Ice AgeWorried about global warming? Talk to a few scientists atWoods Hole. Oceanographers there are seeing big troublewith the Gulf Stream, which warms both North Americaand EuropeBy Brad Lemley
http://www.discover.com/sept_02/main.htmlhttp://www.discover.com/sept_02/main.html


29/94

William Curry is a serious, sober climate scientist, not an art critic.But he has spent a lot of time perusing Emanuel Gottlieb Leutze'sfamous painting "George Washington Crossing the Delaware," whichdepicts a boatload of colonial American soldiers making their way toattack English and Hessian troops the day after Christmas in 1776."Most people think these other guys in the boat are rowing, but theyare actually pushing the ice away," says Curry, tapping his finger ona reproduction of the painting. Sure enough, the lead oarsman is

bashing the frozen river with his boot. "I grew up in Philadelphia.The place in this painting is 30 minutes away by car. I can tell you,

this kind of thing just doesn't happen anymore."But it may again. Soon. And ice-choked scenes, similar to those

immortalized by the 16th-century Flemish painter Pieter Brueghelthe Elder, may also return to Europe. His works, including the 1565masterpiece "Hunters in the Snow," make the now-temperateEuropean landscapes look more like Lapland.

Such frigid settings were commonplace during a period datingroughly from 1300 to 1850 because much of North America andEurope was in the throes of a little ice age. And now there is

mounting evidence that the chill could return. A growing number ofscientistsincluding many here at Curry's base of operations, theWoods Hole Oceanographic Institution on Cape Cod inMassachusettsbelieves conditions are ripe for another prolongedcooldown, or small ice age. While no one is predicting a brutal icesheet like the one that covered the Northern Hemisphere withglaciers about 12,000 years ago, the next cooling trend could dropaverage temperatures 5 degrees Fahrenheit over much of the UnitedStates and 10 degrees in the Northeast, northern Europe, andnorthern Asia.

"It could happen in 10 years," says Terrence Joyce, who chairs theWoods Hole Physical Oceanography Department. "Once it does, itcan take hundreds of years to reverse." And he is alarmed that

Americans have yet to take the threat seriously. In a letter to TheNew York Times last April, he wrote, "Recall the coldest winters inthe Northeast, like those of 1936 and 1978, and then imaginerecurring winters that are even colder, and you'll have an idea of

what this would be like."A drop of 5 to 10 degrees entails much more than simply bumping

up the thermostat and carrying on. Both economically andecologically, such quick, persistent chilling could have devastating


30/94

consequences. A 2002 report titled "Abrupt Climate Change:Inevitable Surprises," produced by the National Academy ofSciences, pegged the cost from agricultural losses alone at $100

billion to $250 billion while also predicting that damage to ecologiescould be vast and incalculable. A grim sampler: disappearing forests,increased housing expenses, dwindling freshwater, lower crop

yields, and accelerated species extinctions.The reason for such huge effects is simple. A quick climate change

wreaks far more disruption than a slow one. People, animals, plants,and the economies that depend on them are like rivers, says thereport: "For example, high water in a river will pose few problemsuntil the water runs over the bank, after which levees can be

breached and massive flooding can occur. Many biological processes

undergo shifts at particular thresholds of temperature andprecipitation."

Political changes since the last ice age could make survival farmore difficult for the world's poor. During previous cooling periods,

whole tribes simply picked up and moved south, but that optiondoesn't work in the modern, tense world of closed borders. "To theextent that abrupt climate change may cause rapid and extensivechanges of fortune for those who live off the land, the inability tomigrate may remove one of the major safety nets for distressed

people," says the report.Still, climate science is devilishly complex, and the onslaught of alittle ice age is not certain, at least at this stage of research. Scientiststhe world over are weighing the potential for rapid North Atlanticcooling, but perhaps nowhere in the United States is more energy,equipment, and brainpower directed at the problem than here at

Woods Hole. The oceanographers on staff subsist largely ongovernment grants and are beholden to no corporation, making thefacility "uniquely independent," says David Gallo, director of specialprojects. Consequently, it should be as likely as any research facilityor university to get at the truth.

The task is huge. Down on the docks where the institution keepsits three research ships, gulls swoop around a collection of massivemetal frameworks; these are core samplers that, dropped over aship's side, can extract long columns of layered sediments from theundersea muck. In a workshop nearby, technicians tinker witharrays of multiple independent water samplers, which at four feetlong and eight inches thick look rather like giant scuba tanks. Out onthe water, researchers drop these instruments into the North

Atlantic, hoping to get a sharper picture of the potential for a littleice age. A sense of urgency propels the efforts. "We need to make


31/94

this a national priority," says Joyce. "It's a tough nut to crack, butwith enough data, I think we can make a more specific and confidentprediction about what comes next." Policymakers armed with aspecific forecast could make adjustments to prepare for theinevitable.

But first things first. Isn't the earth actually warming?Indeed it is, says Joyce. In his cluttered office, full of soft light

from the foggy Cape Cod morning, he explains how such warmingcould actually be the surprising culprit of the next mini-ice age. The

paradox is a result of the appearance over the past 30 years in theNorth Atlantic of huge rivers of freshwaterthe equivalent of a 10-foot-thick layermixed into the salty sea. No one is certain wherethe fresh torrents are coming from, but a prime suspect is melting

Arctic ice, caused by a buildup of carbon dioxide in the atmospherethat traps solar energy.

The freshwater trend is major news in ocean-science circles. BobDickson, a British oceanographer who sounded an alarm at aFebruary conference in Honolulu, has termed the drop in salinity

and temperature in the Labrador Seaa body of water betweennortheastern Canada and Greenland that adjoins the Atlantic"arguably the largest full-depth changes observed in the moderninstrumental oceanographic record."

The trend could cause a little ice age by subverting the northernpenetration of Gulf Stream waters. Normally, the Gulf Stream, laden

with heat soaked up in the tropics, meanders up the east coasts ofthe United States and Canada. As it flows northward, the streamsurrenders heat to the air. Because the prevailing North Atlantic

winds blow eastward, a lot of the heat wafts to Europe. That's why

many scientists believe winter temperatures on the Continent are asmuch as 36 degrees Fahrenheit warmer than those in North Americaat the same latitude. Frigid Boston, for example, lies at almostprecisely the same latitude as balmy Rome. And some scientists saythe heat also warms Americans and Canadians. "It's a real mistake tothink of this solely as a European phenomenon," says Joyce.

Having given up its heat to the air, the now-cooler water becomesdenser and sinks into the North Atlantic by a mile or more in aprocess oceanographers call thermohaline circulation. This massive

column of cascading cold is the main engine powering a deepwatercurrent called the Great Ocean Conveyor that snakes through all the


32/94

world's oceans. But as the North Atlantic fills with freshwater, itgrows less dense, making the waters carried northward by the GulfStream less able to sink. The new mass of relatively fresh water sitson top of the ocean like a big thermal blanket, threatening thethermohaline circulation. That in turn could make the Gulf Streamslow or veer southward. At some point, the whole system couldsimply shut down, and do so quickly. "There is increasing evidencethat we are getting closer to a transition point, from which we can

jump to a new state. Small changes, such as a couple of years ofheavy precipitation or melting ice at high latitudes, could yield a bigresponse," says Joyce.

In her sunny office down the hall, oceanographer Ruth Curryshows just how extensive the changes have already become. "Look at

this," she says, pointing to maps laid out on her lab table. "Orangeand yellow mean warmer and saltier. Green and blue mean colderand fresher." The four-map array shows the North Atlantic eachdecade since the 1960s. With each subsequent map, green and bluespread farther; even to the untrained eye, there's clearly somethingawry. "It's not just in the Labrador Sea," she says. "This cold,freshening area is now invading the deep waters of the entiresubtropical Atlantic."

"You have all this freshwater sitting at high latitudes, and it can

literally take hundreds of years to get rid of it," Joyce says. So whilethe globe as a whole gets warmer by tiny fractions of 1 degreeFahrenheit annually, the North Atlantic region could, in a decade,get up to 10 degrees colder. What worries researchers at Woods Holeis that history is on the side of rapid shutdown. They know it hashappened before.

On the northwest side of Woods Hole's Quissett campus, in a dimlaboratory that smells like low tide, about 24,000 polycarbonatetubes full of greenish-tan mud rest in wire racks, as carefullycataloged as fine wines. They are core samples collected fromseafloors, many collected during expeditions by the Knorr, one of

Woods Hole's three largest research ships. Each core tells a storyabout time and temperature spanning thousands of years.

But one particular core, kept carefully refrigerated at 39 degreesFahrenheit, was pivotal for reaching the conclusion that little ice

ages can start abruptly. The Canadian ship CSSHudson collected thecore in 1989 from a seafloor plateau called the Bermuda Rise in the


33/94

northern Sargasso Sea, roughly 200 miles northeast of Bermuda."It's a peculiar place on the seafloor where mud accumulatesrapidly," says Lloyd Keigwin, a senior scientist in the Woods HoleGeology and Geophysics Department. Most of the sediment was

washed out of Canadian rivers before settling, so it bears witness tothe vagaries of climate in the North Atlantic.

Seafloor sediments are peppered with tiny invertebrates calledforaminifera, which Keigwin describes as "amoebas with shells," thatcan yield clues about the temperature of the ocean in which theylived. Clay and silt from the Nova Scotia region cause the littlecreatures to accumulate in neatly distinguishable layers, whichmeans a wealth of information.

Keigwin subjected the foraminifera in various layers of this core to

mass spectroscopic analysis. By measuring the proportions ofoxygen isotopesespecially the ratio of oxygen 16 to oxygen 18he

was able to peg the temperature at which the tiny animals in eachlayer formed their calcium carbonate shells to an accuracy of lessthan 1 degree Fahrenheit. He coupled that with carbon dating todetermine each sediment layer's age.

Keigwin had expected to find evidence of climate swings duringthe past few thousand years. But in the CSSHudson's prize sample,

which was drilled with a more precise corer than oceanographers

had used previously, he uncovered plenty of data about abrupttemperature changes over the past 1,000 years, including for a littleice age that averaged about 4 degrees Fahrenheit colder than thepresent. "And because the Sargasso Sea is pretty well mixed, thecooling must have been widespread," Keigwin says. More ominously,"I found evidence that proves the climate cycles continue right upuntil today."

Clearly, the little ice age from 1300 to 1850 wasn't kicked off byhumans releasing greenhouse gases into the atmosphere. Butnatural climate cycles that melted Arctic ice could have causedthermohaline circulation to shut down abruptly. "We are almostcertain that this was the cause of the last little ice age," says RuthCurry, "although we'd need a time machine to be sure."

"I was aware that this could be a bombshell, but I stuck my neckout," says Keigwin, who first published his findings in 1996. Sincethen, similar high-sediment locations have bolstered his earlyconclusions. "As it turns out, there are probably at least 10 places inthe North Atlantic that can give you pretty good core evidence ofmini-ice-age cooling," he says.

A more recent event is perhaps better evidence that a climate cancool quickly because of thermohaline shutdown. In the late 1960s, a


34/94

huge blob of near-surface fresher water appeared off the east coast ofGreenland, probably the result of a big discharge of ice into the

Atlantic in 1967. Known as the Great Salinity Anomaly, it driftedsouthward, settling into the North Atlantic in the early 1970s. Thereit interfered with the thermohaline circulation by quickly arrestingdeepwater formation in the Labrador Sea. It continued to drift in acounterclockwise direction around the North Atlantic, re-enteringthe Norwegian Sea in the late 1970s and vanishing soon after.

"I believe it shut the system down for just a few years. The resultwas very cold winters, particularly in Europe," says Ruth Curry.

That fresher-water mass, fortunately, was small enough todisperse in a short period of time. The one accumulating up therenow, however, "is just too big," says Joyce.

Climate science is extraordinarily complex because it is dependentupon the gathering and interpretation of millions of data points. Ifthe National Weather Service has trouble predicting tomorrow's

weather, how can anyone forecast a change in global climate a fewyears hence? One answer is even more data. At the moment, thereare about 450 floating sensors bobbing around in the Atlanticmonitoring temperature and salinity changes, and that is notenough, says Ruth Curry. "The models don't have enough resolutionto capture all the physics yet. Prediction is tough."

Or maybe Woods Hole researchers are adhering to a flawedmodel. That's the view of Richard Seager, a climate scientist atColumbia University's Lamont-Doherty Earth Observatory. In apaper titled "Is the Gulf Stream Responsible for Europe's Mild

Winters?" to be published this year in the Quarterly Journal of theRoyal Meteorological Society, he casts doubt on the notion thatwarmth transported by the Gulf Stream has a significant impact oneither continent. Europe would be warmer, he says, "even if the

Atlantic were just a big, stagnant ocean" because the prevailingwesterly winds would still blow heat stored in the Atlantic in thesummer to Europe in the winter. Transported Gulf Stream heat, hesays, accounts for less than 10 percent of England's warmth relativeto the United States.

In Seager's view, prolonged winter warmth is more likely than alittle ice age. "The thousand-pound gorilla in eastern North Americaand Europe is the North Atlantic Oscillation," he says. This is acomplex, poorly understood variation in the strength of air-pressurecells over Iceland and the Azores. When pressure over Iceland ishigh, the pressure over the Azores tends to be low, and vice versa.

During the winter, a lower-than-usual low over Iceland and a higher-than-usual high over the Azores forces cold air to eastern Canada


35/94

and warm, moist air to northwestern Europe and the eastern UnitedStates.

That's precisely what has happened from the 1960s to the late1990s, says Seager, which gave rise to relatively balmy winters in thehigh-population regions on both sides of the Atlantic. "If this phasecontinues, as some models predict will occur as the result of risinggreenhouse gases, this would make these changes in winter climatepersist for years to come," he says.

Seager's viewpoint is in the minority. In other models, and climatescience is ultimately a battle of different computer models, the GulfStream is a major source of warmth for the lands that border theNorth Atlantic. In Ruth Curry's view, the science as it stands is morethan strong enough to warrant thinking ahead.

"We can't know the point at which thermohaline shutdown couldactually start," she says. "But we should plan for it."

Cold Brutality

Should a little ice age arrive, its impact will be told in humansuffering, not scientific terminology. The Little Ice Age (Basic Books,

2000), by anthropology professor Brian Fagan of the University ofCalifornia at Santa Barbara, is replete with tales of woe depicting theplight of European peasants during the 1300to 1850 chill: famines, hypothermia, breadriots, and the rise of despotic leaders

brutalizing an increasingly dispiritedpeasantry. In the late 17th century, writesFagan, agriculture had dropped off sodramatically that "Alpine villagers lived on

bread made from ground nutshells mixed

with barley and oat flour." Finland lostperhaps a third of its population to starvationand disease.

Life was particularly difficult for those wholived under the constant threat of advancingglaciers in the French Alps. One, the Des Boisglacier on the slopes of Mont Blanc, was saidto have moved forward "over a musket shoteach day, even in the month of August."

When the Des Bois threatened to dam up theArve River in 1644, residents of the town of

Opposite: "Thephysics of El Nioare simplecompared to thephysics of thisclimate change,"says TerrenceJoyce, chairmanof the WoodsHole Departmentof PhysicalOceanography,with Ruth Curry,one of the leadresearchers.

Photograph by GregMiller


36/94

Chamonix begged the bishop of Geneva to petition God for help. Inearly June, the bishop, with 300 villagers gathered around him,

blessed the threatening glacier and another near the village of

Largenti

re. For a while, salvation seemed at hand. The glaciersretreated for about 20 years, until 1663. But they had left the land sobarren that new crops would not grow. B. L.

THE BIBLE -- Science or Superstition?

Is the Bible a record of science or a relic of ancientmythology?Is the Bible relevant to the Space Age? or obsoletefolklore?Here is the most incredible, asonishing PROOF,from history,physics, astronomy, geology, chemistry,oceanography, andarchaeology that the Bible, written thousands of

years ago,contains knowledge that was supposedly onlydiscovered byscientists during the past two centuries! Here isPROOF theBible IS not only the "divine revelation" of aCreator God,

but that forebears were highly intelligent, skillfuland astutescientists, navigators, and explorers. Here is the

most amazingand intriguing story you have ever heard -- provingthe Bibleto be an astounding scientific chronicle -- and aBook ofDivine inspiration and insight!

William F. Dankenbring

FOR CENTURIES, skeptics and scoffers have called the Bible acollection of ancient primitive myths, fables, stories, and


37/94

superstition. One religious leader calmly claimed, "We know nowthat every idea in the Bible started from primitive and childlikeorigins . . . ."

Dr. Edgar J. Goodspeed, who translated the Bible into English,declared that the book of Joshua "is the legendary story of theconquest of Canaan" and the book of Ruth "belongs to Israel'sfiction, rather than to its history, and should be among its tales andstories."

WHY have so-many men of high education, scholars, and scientistsREJECTED the Bible as historical truth and reliable science? Is theBible "unscientific"?

It is time you knew the incredible truth!

Science Versus Myth

We live in a modern, push-button, scientific world. Science isadulated, placed on a lofty pedestal, and virtually worshipped as thenew "messiah" -- the new savior of the world.

However, science has also bequeathed to the world lethal modernweapons of war -- the H-bomb, Neutron bomb, A-bomb, poisonous

gases, deadly chemicals -- a murderous host of technologicallyamazing devices to destroy!

Science has been described as an angel of mercy, and also as a devilof destruction.

But unknown to millions, the Bible has a great deal to say aboutTRUE science. And it also has much to say about the wrong kind ofscience, and 'science falsely so called"! Although the Bible is not a

textbook about science, it does give many foundational principles ofscience -- alludes to basic principles of biology, physics, chemistry,meteorology, astronomy, geology, and oceanography, as well asmedical science and health sciences!

Those who have lightly discarded the Bible and relegated it to thelimbo of outer darkness, as myth and fable, have carelessly missedout on the solid foundation of SCIENCE in the Bible! They have

jumped to conclusions without getting all the facts.


38/94

For some reason, the world of scholars and scientists has rejectedthe Bible as the provable Word of the living God -- withoutexamining all the evidence!

Very few know it, but the Bible has far more to say about sciencethan many suppose. Scientific facts, not understood by the worlduntil the last few hundred years, with the advent of the "scientificexplosion," are plainly and directly mentioned IN THE BIBLE!

Think what this means. While pagans worshipped sticks and stones,the sun, moon, and stars; while entire nations were bowing under acloud of magic and superstition, ignorant of the truth -- at that verysame time, a Book unknown to millions, the Bible -- the Book of

books -- was being INSPIRED which contained many fascinating,

fantastic SCIENTIFIC SECRETS totally unknown to the rest of theworld!

Notice how amazingly scientific the Bible really is!

Flat Earth Theory

Many people have erroneously believed that the Bible teaches theearth is flat. The Medieval Catholic Church held to the notion theearth is flat and is the center of the universe.

When Galileo presented scientific evidence to the contrary, his factsand theories were branded as "absurd in philosophy, and formallyheretical, because expressly contrary to Holy Scripture."

But nowhere does the Bible teach the flat earth theory, or that theearth is a stationary object at the center of the universe.

Galileo's theories were declared heretical in the 17th century. But,

amazingly enough, six hundred years before Christ, the prophetIsaiah was inspired by Almighty God to write and speak ef thespherical shape of the planet earth!

Notice it! In Isaiah 40:22 we read of God, "It is He that sitteth uponthe CIRCLE of the earth." Moffatt translates this verse more clearly:"He sits over the ROUND EARTH." The Critical and ExperimentalCommentary states this expression is "applicable to the globularform of the earth." The original Hebrew word is chuug and means a"compass, circle, or sphere."


39/94

But how did Isaiah, an ancient Hebrew prophet, know that the earthis round? Here is PROOF that the ancient Hebrews were far moreknowledgeable and scientific than they are given credit for being!

But how much did the ancient writers of the Bible really know aboutthe earth? Did they believe the notions of their Gentilecontemporaries who believed the earth was carried about on the

back of a great tortoise?

The Amazing Earth

Three amazing truths were known about the earth itself which therest of the world did not understand for another two or threeTHOUSAND YEARS! Sound incredible? It should!

First, the fact that the earth revolves around the sun once every yearwas not generally understood until the days of Copernicus and cameto be known as the Copernican Theory. This was in the 16th century-- just a little more than 400 years ago. He taught that the sun is thecenter of the solar system.

However, thousands of years before his time,-in the days of thepatriarch Moses, the Bible uses the precise expression to indicate therevolution of the earth around the sun once a year was known toancient Biblical astronomers! In Exodus 34:22 we read, in the KingJames Version, the innocent phrase, "And thou shalt observe thefeast of weeks, of the firstfruits of wheat harvest. and the feast ofingathering at the year's end." According to the original Hebrew,however, this should be translated "at the REVOLUTION OF THE

YEAR." The original Hebrew word is tequuphah and means "to movein a circle," "circuit," "to go round," "orbit of the sun," as well as"revolution of time."

The Goodspeed translation has "at the turn of the year." In the daysof the prophet Samuel, the expression "in revolution of days" wasused to denote the time from conception to birth of a child (I Sam.1:20, margin). Goodspeed translates this, "when the time camearound."

Notice also II Chronicles 24:23 where the "end of the year" is called,in the original Hebrew, "in the REVOLUTION of the year" (marginalrendering). Don't these verses clearly suggest the fact that theancient Hebrews KNEW the earth revolves around the sun, andcompletes one revolution -- one turning -- each year?


40/94

But this is not all. Notice Job 38:12-14 where we read: "Hast thoucommanded the morning since thy days; and caused the dayspringto know his place; that it might take hold of the ends of the earth . . .IT [the earth] IS TURNED AS CLAY TO THE SEAL . . ."

What does this mean? God is talking to the ancient patriarch Jobabout the morning -- the rising of the sun. How is it that the sunappears to rise in the morning? This verse contains the scientifictruth -- the TRUE explanation! The earth tself turns, or "rotates" -from west to east, causing the sun to rise in the morning, in theeastern sky, and appear to move through the sky to the westernhorizon, where it appears to "set."

The original Hebrew in this verse says, of the earth, "it turns itself."

What could be a more apt expression? The allusion to the day andthe seal refers to the rolling cylinder seal one to three inches long,such as was used in ancient Babylon, which left its plasticimpression on the clay as it turned about or rolled around. Whatmore apt figure of speech could be used to represent the motion ofthe earth itself, as it rotates, causing day and night?

Thirdly, the laws of gravity were not explained and understood untilSir Isaac Newton, a Christian scientist and theologian, discovered

them in the 18th century. The laws of motion were discovered by thissame genius.

However, strange as it may seem, thousands of years ago the Biblealluded to the laws of centrifugal force, centripetal force, gravity, andmotion! How else do you explain the enigmatic statement in the

book of Job, speaking of the earth -- "He [God] . . . hangeth the earthUPON NOTHING"? (Job 26:7.)

The pagans believed a tortoise carried the earth about; but God

revealed to His people the truth -- that the earth hangs suspended inspace by powerful laws of force and motion!

God asked Job, "Where wast thou when I laid the foundations of theearth? . . . Whereupon are the foundations [sockets] thereof fastened(made to sink]?" (Job 38:4, 6.) It is interesting that science hasdiscovered that the earth's axis is pointed in the general direction ofthe North Pole Star, and the north and south poles are the points

where the earth's axis of rotation meets the surface of the earth. The

earth is inclined to its axis at 23 1/2 degrees. God is the One who


41/94

planned it all out; set the earth to spinning on its axis; and pointedthe north pole toward the star Polaris.

Science of Meteorology

The science of weather and understanding the earth's atmosphere isof relatively recent origin. It, too, has developed greatly during thelast two hundred years. Chemistry and physics play a vital role inthis science. Before the nature of matter and air were understood,

weather science was in total chaos.

Here again, however, the Bible "scooped" science by more than twothousand years!

The basic key to understanding the weather cycles and patterns onthe earth is the hydrological cycle. Today it is well known that waterevaporates from the surface of the oceans, rivers, lakes and all

bodies of water; that it rises into the atmosphere; and that later itreturns to the earth as rain, snow, sleet, or hail. The evaporation-condensation-precipitation cycle was not understood by mankind,however, before the nature of water, water vapor, and the chemistryof matter was understood.

The Bible, however, reveals this basic CYCLE was understood,THOUSANDS of years ago! Once again, the Bible is proved to beSCIENTIFIC! Notice Jeremiah l0:13 -- "When he uttereth his voice,there is a multitude of waters in the heavens, and he causeth the

vapours to ASCEND from the ends of the earth."

Tell me -- how could Jeremiah, a prophet of God, have possiblyknown about the evaporation of water into water vapor,condensation of water vapor as rain droplets, and the precipitationcycle? Was he an inspired scientist as well as a prophet?

Jeremiah was not the only Biblical meteorologist, however. Solomonwas also an expert in understanding the weather cycle. TheScriptures reveal that king Solomon was an avid student of nature,and the natural world, and wrote extensively on the subject. Some ofhis writings as a "naturalist" are preserved in the Scriptures.

Wrote Solomon about one thousand years before Christ, "The windgoes to the south, and circles about continually, and on its circlingsthe wind returns again. All the rivers run into the sea, yet the sea is


42/94

not full; unto the place from which the rivers come, to there andfrom there they return again" (Eccl. 1:6-7, Amplified Version).

Solomon understood the circuits of the wind -- and of water. Howdid he know? Was he merely guessing? Or was he not truly one ofthe most gifted, wisest men of all history? If we give BenjaminFranklin credit for being a gifted genius, how much more should werecognize the genius of Solomon who was the most famousnaturalist, writer, poet, composer, and scientist of his time?(compare I Kings 4:29-34.)

Consider, for a moment, how incredibly amazing Solomon'sknowledge was. It was not until the 1800's that William Ferrell, an

American meteorologist, formulated "Ferrell's law" which explains

the prevailing directions of the winds over the earth, based on thecarth's rotation.

Said Matthew Fontaine Maury, an American hydrographer who livedin the late 1800's, "The direction in which a wind blows is soconstantly changing that we often speak of the winds as fickle,inconstant, and uncertain. There is, however, ORDER in themovements of the atmosphere. The fickle winds are obedient toLAWS."

The Sea Around Us

In Job 38:16, God asked, "Have you explored the springs of the sea?Or have you walked in the recesses of the deep?" (Amplified

Version).

How could the writer of the book of Job have known that beneaththe oceans of the world there exist springs, or fountains of FRESH

WATER? An article in the Saturday Review (July 1, 1967) declared:

"Although they usually remain undetected, submarine springs offresh water are often more common along certain types of shorelinethan are rivers and other surface streams." Along some shorelines,as much as 20 million gallons of fresh water a day flows into the seafor every mile of shoreline.

In fact, one major submarine spring in the Persian Gulf flows withenough volume to create a large area of fresh water in the midst ofthe sea, because of favorable limestone geology in Iran and Saudi

Arabia. In Greece, an estimated 100 million cubic feet of fresh watergoes into the sea through submarine springs.


43/94

But about four thousand years before, God asked Job if he knewabout the springs in the sea!

INCREDIBLE!

Job was also told about the "recesses of the deep." Oceanographerstoday have plotted much of the ocean bottoms of the world, and havediscovered deep underlying "trenches" which at some points godown thousands of feet in sharp, sudden drop-offs. Yet even Jobknew of the existence of "recesses" in the oceans! The MarianaTrench in the Pacific Ocean is 36,198 feet deep. It was discovered inSeptember, 1959 by the Soviet ship Vityaz. The same ship discovereda depth of 35,702 feet for the Tonga Trench; there are four otherdeep trenches in the North Pacific. The greatest depth in the Atlantic

Ocean is north of Puerto Rico -- the Puerto Rico Trench, 27,498 feetdeep.

The dark world of the bottom of the ocean is now being explored byscientists in bathyscaphes, and special cameras, mounted withstrobe lamps, have been lowered miles into the depths. Newinstruments have revealed that the ocean bottom is surprisinglyrugged. Depths of valleys and canyons running underwater whenaveraged out are five times greater than heights reached on

continents. The undersea world is cut, and sliced, by huge canyonsbigger than the Grand Canyon. One such canyon is the HudsonCanyon off New York. Sixty miles off shore, this mammoth canyonknifes downward to 8000 feet, and then slopes on down to 6,500feet.

The sea floor is called the abyssal plains. At their edge are sometimesfound tremendous chasms or trenches, averaging 20 miles wide atthe top and hundreds of miles long. The deepest such trenchdiscovered is the Challenger Deep in the Marianas Trench, almost

seven miles down.

Yet thousands of year ago, God asked the patriarch Job what heknew about these "recesses" or "TRENCHES" of the "deep" -- that is,of the Oceans? How could Job have known? In the original Hebrew,the word for "explore" or "search out" is cheger and means to"search out, examine; secret, inmost part." The word for "deep" istehown and means "confusion" -- or "the ABYSS, the great deep."


44/94

How could such graphic words have been written which so aptlydescribe the ocean bottom -- so many thousands of years ago --unless they had been inspired by God?

"Pathfinder of the Seas"

Matthew Fontaine Maury, when reading the Bible, was, struck by thewords of Psalm 8:8 -- "The fowl of the air, and the fish of the sea,and whatsoever passeth through the paths of the seas." His curiosityaroused, he set out to map the currents of the oceans of the worldand became the foremost hydrographer of his day (1806-1873). Hediscovered the ocean routes which would make best use of prevailingocean currents and winds. His research enabled ship owners to cutmany days from the time required to make their voyages and helped

them save many thousands of dollars. He was called the "Pathfinderof the Seas." The Bible was his source of inspiration!

But how did king David, who wrote the eighth Psalm -- who livedabout one thousand years before Christ -- know about the "paths ofthe seas" and the great currents in the oceans?

The Gulf Stream

In 1855 Matthew Fontaine Maury, pioneer oceanographer, wrote,"There is a river in the ocean. In the severest droughts it never fails,and in the mightiest floods it never overflows. Its banks and its

bottom are of cold water, while its current is of warm. The Gulf ofMexico is its fountain, and its mouth is in the Arctic Seas. It is theGulf Stream" (The Physical Geography Of the Sea, 1855).

Truly, a river in the middle of the sea, the Gulf Stream flows for themost part through the Caribbean into the Gulf of Mexico and leavesthrough theStraits of Florida, from where it flows out into the broad

Atlantic across to northwestem Europe.

"Seaward of New England, where the Gulf Stream is mostrobust, it can be l00 miles wide and 16,400 feet deep, and havea surface velocity of six miles an hour. There it carries past agiven point about 150,000,000 tons of water every second;this makes it the equal of 700 Amazons or 8,800 Mississippis'"("A Capsule History of the Gulf Stream," by ThomasLineaweaver III, Holiday, Nov. 1967).


45/94

If the Gulf Stream were emptied upon the United States, it wouldflood the entire nation to a depth of over four feet -- in just one day!This mighty river is truly a PATHWAY in the sea! The larvae of asnail (Cymatium Parthenopeum) found from Brazil to the west coast

of Africa ride the Gulf Stream, pe

Climate Effects of Volcanic Eruptions

Documents

Transcript of Climate Effects of Volcanic Eruptions